Question

The process of formation of colloidal gel from calcium silicate and aluminates is:

• A. endothermic
• B. exothermic
• C. reversible
• D. both $B$ and $C$

Answer 1

Answer: (B)

exothermic

The first stage of hydration is characterized by the rapid dissolution of clinker

${Ca}_{3}Si{O}_5+3H_{2}O⟶3{Ca}^{2+}+4{OH}^{-}+H_{2}Si{O}_2^{4-}$

immediately after the wetting of the clinker powder. In calorimetry measurements, a large exothermic signal is measured due to wetting and dissolution of clinker. The wet clinker releases ions such as calcium, silicate and hydroxide to the solution. From the evolution of these ion concentrations the dissolution rate of clinker can be evaluated.